57 lines · cpp
1//===- ReduceGlobalVars.cpp - Specialized Delta Pass ----------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements a function which calls the Generic Delta pass in order10// to reduce Global Variables in the provided Module.11//12//===----------------------------------------------------------------------===//13 14#include "ReduceGlobalVars.h"15#include "Utils.h"16#include "llvm/IR/Value.h"17#include "llvm/Transforms/Utils/Cloning.h"18#include "llvm/Transforms/Utils/ModuleUtils.h"19 20using namespace llvm;21 22static bool shouldAlwaysKeep(const GlobalVariable &GV) {23 return GV.getName() == "llvm.used" || GV.getName() == "llvm.compiler.used";24}25 26/// Removes all the GVs that aren't inside the desired Chunks.27void llvm::reduceGlobalsDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {28 Module &Program = WorkItem.getModule();29 30 // Get GVs inside desired chunks31 std::vector<Constant *> InitGVsToKeep;32 for (auto &GV : Program.globals()) {33 if (shouldAlwaysKeep(GV) || O.shouldKeep())34 InitGVsToKeep.push_back(&GV);35 }36 37 // We create a vector first, then convert it to a set, so that we don't have38 // to pay the cost of rebalancing the set frequently if the order we insert39 // the elements doesn't match the order they should appear inside the set.40 DenseSet<Constant *> GVsToKeep(InitGVsToKeep.begin(), InitGVsToKeep.end());41 42 // Delete out-of-chunk GVs and their uses43 DenseSet<Constant *> ToRemove;44 for (auto &GV : Program.globals()) {45 if (!GVsToKeep.count(&GV))46 ToRemove.insert(&GV);47 }48 49 removeFromUsedLists(Program,50 [&ToRemove](Constant *C) { return ToRemove.count(C); });51 52 for (auto *GV : ToRemove) {53 GV->replaceAllUsesWith(getDefaultValue(GV->getType()));54 cast<GlobalVariable>(GV)->eraseFromParent();55 }56}57